The preparation of alumina through a precipitation process is taught in U.S. Pat. Nos. 4,154,812; 6,174,511; and 4,248,852, all of which are hereby incorporated by reference for all purposes.
U.S. Pat. No. 4,154,812 teaches a process whereby a highly diluted mixture of seeds is prepared by adding an initial charge of aluminum sulfate solution to a heel of water in an amount sufficient to adjust the pH to a value from about 2 to a value of about 5. For this material the acidity of the seed solution is an important property. The aluminium sulfate hydrolyses and forms very small crystallites of boehmite. The nucleation process of the seeds takes place very rapidly. Subsequently, the mixture is neutralized by simultaneously adding a solution of sodium aluminate and a solution of aluminum sulfate. The control of the pH, the temperature, the reactants, and the feed rates are strictly controlled during the precipitation strike. Then the slurry is aged. After filtration and washing the slurry is finally dried.
The present invention teaches a more efficient process which has a beneficial effect on the pore volume. Specifically, the process of the present invention produces a unique, highly porous, crystalline, semi-boehmite powder with superior thermal stability and high surface area at elevated calcining temperatures.